1. Field of the Invention
The present invention relates generally to telephone systems, and more particularly to a method of local emergency call detection and notification for telephone sets that communicate with a remote telephone system via an analog line interface module (LIM).
2. Description of the Related Art
Recent advances in communications technology have supported an increase in the number of enterprise employees and contractors who work away from the geographical location of the enterprise (e.g. in a Small-Office/Home-Office (SOHO)). In such circumstances, a teleworker may utilize a telephone that incorporates a selectable analog line interface module (LIM) for connection to a local central office (CO) or alternatively may communicate with the enterprise (e.g. Integrated Communications Platform (ICP)) via a secure digital voice connection (i.e. VoIP). Thus, the LIM device is capable of providing local E-911 call routing to the connected CO. Local E-911 call routing can be initiated by lifting the handset and selecting the analog line (possibly selected by default), in response to which dial tone is provided by the CO and the user is permitted to dial 911.
Support of Emergency Services requires an Emergency Location Identification Number (ELIN) number to be sent to a Public Safety Answering Point (PSAP) when an emergency service number (e.g. 911) is dialed. The TIA standard prescribes al 10-digit number that is inserted in the source address field on E911 trunk calls. The PSAP uses the ELIN to direct emergency personnel to the location of the call. The ELIN acts as an index into the civic location database maintained at the PSAP, which in turn contains the real callback number, street address, in-building coordinates, etc. of the caller.
Thus, when a caller dials 911, a call is made to the PSAP office, and information regarding the phone's location is sent to the PSAP to allow emergency response professionals to locate the individual making the call. The location information is represented by the 10 digit ELIN number.
When the user has not selected the analog line to make an E-911 call and the attached telephone set is connected to the enterprise, call processing within the ICP handles the E-911 call using existing system E-911 call routing. However, the enterprise ICP system may be located in a different PSAP coverage area than the telephone set, or the PSAP may not have accurate location information for the telephone set. In either of these cases, routing an emergency call through the enterprise system may result in a delayed or misdirected emergency response.
As indicated above, local E-911 call routing can be initiated by lifting the handset and selecting the analog line. However, the user may not remember to select the analog line during an emergency. Also, someone who is not familiar with the need to first select the analog line may dial the emergency call.